It is increasingly common for people to use client-side devices to communicate via a radio access network (RAN) with other devices, whether those devices are directly connected to the same RAN or to another network (such as another RAN or a transport network, as examples) to which that RAN directly or indirectly provides access. These client-side devices are generally referred to in this disclosure as access terminals, though this term is intended to broadly encompass various devices known by terms such as mobile stations, mobile devices, user equipment, wireless-communication devices, cellphones, smartphones, personal digital assistants (PDAs), tablets, laptops, air cards, Universal Serial Bus (USB) devices (e.g., dongles), and/or any other device(s) capable of functioning as an access terminal according to this disclosure. Via the RAN, access terminals generally engage in communications such as voice calls, packet-data sessions, text messaging (e.g., Short Message Service (SMS) messaging), and the like.
Furthermore, the wireless communication between the RAN and an access terminal is typically bidirectional in nature. The component of that communication that is sent from the RAN to the access terminal is described as being sent on what is known as the forward link, while the component that is sent from the access terminal to the RAN is described as being sent on what is known as the reverse link. On both links, the wireless communications are typically formatted in accordance with a wireless-communication protocol, one example type of which is code division multiple access (CDMA), where CDMA networks that operate according to industry specifications (IS) such as IS-95 and IS-2000 are often referred to as 1xRTT (or “1x”) networks, where 1xRTT stands for Single Carrier Radio Transmission Technology.
Some RANs operate in accordance with a particular type of CDMA protocol known as Evolution Data Optimized (EV-DO). These RANs are generally configured to operate according to one or more versions of IS-856, and are designed to provide high-rate packet-data service to access terminals using a technique on the forward link known as time-division multiplexing (TDM) and using what is essentially 1x technology on the reverse link. More generally, RANs can be arranged to operate according to any of numerous other protocols, some examples of which are Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), WiMAX (IEEE 802.16), time division multiple access (TDMA), Global System for Mobile Communications (GSM), Wi-Fi (IEEE 802.11), and the like.
In RANs that are of a type known as wireless wide area networks (WWANs) (or cellular wireless networks), the entities with which access terminals communicate over the air interface are known by terms such as base station and access node, terms that are used at different times in different ways to refer to different entities. For example, the term base station is sometimes used to refer simply to a device also known as a base transceiver station (BTS), which contains the hardware, antennas, and other components that cooperate to actually conduct the over-the-air (OTA) communication with the access terminals on behalf of the RAN. In LTE networks, a BTS is typically referred to as an eNodeB, which stands for Evolved Node B, named as being an evolved version of a Node B in a UMTS Terrestrial RAN (or UTRAN). At times, however, the term base station or access node is used to refer in combination to (i) one or more BTSs and (ii) a device known as a base station controller (BSC) (or radio network controller (RNC)), which controls the BTS(s) and connects it (them) to the rest of the network and beyond.
Typically, the various base stations in a RAN are deployed in various locations in many different cities and other areas, with the aim of effectively blanketing such geographical areas with sufficient wireless coverage. As such, multiple wireless coverage areas (e.g., cells, sectors, and the like) in which a RAN provides wireless service are quite often adjacent to one another.